Carburetor de-icing



United States Patent Oflice 3,257,179 Patented June 21, 1966 3,257,179 CARBURETOR DE-ICING Lawrence L. Bott, Oak Park, Ill., assignor to N alco Chemical Company, Chicago, Ill., a corporation of Delaware No Drawing. Filed Feb. 21, 1963, Ser. No. 260,331 11 Claims. (Cl. 4463) This invention is concerned with the chemical treatment of volatile hydrocarbon fuels used in the operation of internal combustion engines to prevent carburetor icing. This application is a continuation-in-part of copending application Serial No. 710,860, which application was filed on January 24, 1958, now abandoned.

The problem of carburetor throttle blade icing and its attendant effect on the operation of internal combustion engines is well known. Poor engine performance in cold weather, as evidenced by stalling and bucking, is an experience shared by many motorists who operate automobiles in many areas where intemperate weather conditions prevail during the winter months.

Five conditions are usually necessary to promote carburetor icing: (1) critical engine type, (2) low engine load, (3) air temperature from approximately 35 to 45 F., (4) 100% humidity and (5) volatile winter-grade gasoline, that is, a gasoline having a Reid vapor pressure of at least lbs/sq. in. at 100 F. (A.S.T.M. Method Designation D 323) and/or having a distillation curve such that at least 50% by volume of said gasoline distills over at 212 F. When these circumstances concur, ice usually forms on the throttle blade and in the throttle blade opening, which in turn causes malfunctioning of the carburetor.

Improved carburetor design has not substantially alleviated this problem. One method of overcoming the diificulty is to add chemical de-icers to the fuel. In most instances, these chemicals are composed of lower monohydric alcohols when used at dosages of 1%2% or more, based on the weight of the fuel. Such large dosages could naturally dilute the fuel, unless care is used in their addition. For this reason, it has become popular to add the de-icer at the refinery level rather than to have service station operators make the addition directly to the fuel tank. It would be a valuable contribution to the art if a de-icing chemical were available which would be effective by adding very small amounts to fuels used in internal combustion engines. An object of the invention, therefore, becomes the provision of a new chemical process for preventing the icing of carburetors.

Another object is to prevent carburetor icing by adding to the fuel small, yet effective, amounts of a chemical de-icer. Other objects will appear hereinafter.

In accordance with the invention, it has been found that carburetor icing may be avoided by adding to the volatile winter-grade fuel burned in internal combustion engines, a de-icing amount of a 1,2-substituted imidazoline polycarboxylic acid salt. Generally, the amount of 1,2-substituted imidazoline polycarboxylic acid salt neces sary to prevent carburetor icing is as little as parts per million. As much as 500 parts per million may be necessary when extremely volatile gasolines are used, but usually about 250 parts per million will give excellent results with most internal combustion engine hydrocarbon liquid fuels.

The 1,2-substituted imidazolines from which the polycarboxylic acid salts are prepared are well known. They are easily synthesized from organic carboxylic acids, particularly fatty acids, and polyamino compounds, in accordance with the teachings of Wilson U.S. Patents 2,267,965 and 2,355,837, the disclosures of which are incorporated herein. The preferred starting fatty acids are those containing from 6 to 24 carbon atoms in chain length. Most preferred are the unsaturated fatty acids containing from 12 to 18 carbon atoms in chain length. In addition to the fatty acids per se, the natural oils and fats or crude mixture of the acids also may be employed.

The polyamino compounds useful in preparing the starting imidazolines are the diamines, e.g., ethylene diamine, the polyalkylene polyamines, e.g., diethylene triamine, triethylene tetramine, tetraethylene pentamine and the hydroxyalkyl alkylene polyamines, e.g., aminoethyl ethanolamine.

In all the cases above, the imidazolines produced are substituted in the 1- position of the imidazoline ring by a monofunctional or polyfunctional radical, save when ethylene diamine is used, in which instance a hydrogen atom is the only suhstituent on the 1- position. In any event, however, the substituents on the 1- position or a hydrogen atom are capable of reacting with such functional organic compounds as acyclic organic acids or alkyl halides to add one or more groups to the imidazoline or substituted imidazoline molecule, hence these compounds may be considered as 1,2-substituted imidazolines.

Illustrative of the substituents that may be added to the imidazoline molecule are the acylation or esterification products formed by reacting an organic acid, such as for instance, a fatty acid with typical imidazolines. If, for instance, Z-heptadecyl imidazoline is reacted with stearic acid, the compound Z-heptadecyl-l-stearoyl imidazoline is produced. The reaction of stearic acid with l-(Z-aminoethyl)-2-heptadecy1 imidazoline would form 1 (2 stearoylaminoethyl) 2 heptadecyl imidazoline. Where a 2-hydroxyethyl group is a substituent at the 1- position, a suitable ester can readily be prepared. Where a primary amino group, as well as one or more secondary amino groups, are positioned as substituents on the 1- position, a number of acylated groups can be attached to the molecule.

The polycarboxylic acids used in preparing the salts may contain more than two carboxylic acid groups, but usually the carboxylic acid groups will not exceed three. These acids should contain at least 6 carbon atoms and, most preferably, 10 or more carbon atoms are desirable. The acids may be aliphatic, carbocyclic or aromatic and may or may not contain nonhydrocarbon substituents. Illustrative acids are sebacic, adipic, pimelic, suberic, azelaic and polymerized olefinic monocarboxylic acids such as dimerized oleic acid.

The preferred salt forming acids are the well known polymerized fatty acids which are formed by the addition polymerization of fatty acids containing at least two olefinic linkages. These acids are carboxylic acids and are usually dimers which contain two carboxylic groups per molecule. In some cases polymerized fatty acids may contain three or more carboxylic acid groups, but they are usually admixed with the dimer in most commercial grades of the acids. A complete discusion of these acids is given in Industrial and Englneering Chemistry, volume 32, No. 6, pages 802-809, and also in Gobel U.S. Patent 2,482,761. The disclosure of these two literature sources are incorporated herein by reference.

Typical specifications on two commercial grades of polymerized fatty acids are given below in Table I:

These commercial acids are not pure, but the dicarboxylate polymers which predominate, contain about 3436 carbon atoms. Composition I is produced in accordance with the teachings of Gobel U.S. 2,482,761 and Composition II is a by-product from the caustic fusion of castor oil in the manufacture of sebacic acid.

Since the acids used are polyfunctional, one mol of acid may combine with as many basic nitrogen atoms as there are available in the particular imidazoline chosen. In the case of imidazolines containing nitrogen in the heterocyclic ring only, one mol of imidazoline will cornbine with one free carboxylic acid group. Preferably, there should be two basic nitrogen atoms of one or' more mols of 1,2-substituted imidazoline combined with one mol polycarboxylic acid. For purposes of simplification, this is hereinafter referred to as there being two mols of imidazoline per mol of polycarboxylic acid in the preferred compositions. Excesses of three mole of imidazoline per mol of acid give no substantial improvements.

Compositions illustrative of the types that may be used in the practice of the invention are shown below by the following general formulae:

where D is a divalent, nonamino organic radical containing less than 25 carbon atoms composed of elements from the group consisting of C, H, O and N. D represents a divalent, organic radical containing less than 25 carbon atoms composed of elements from the group consisting of C, H, O and N and contains at least one amino group. R may be hydrogen or a higher aliphatic group containing from 5 to 23 carbon atoms. R must have at least one occurrence where it is a higher aliphatic group of the type described. Y and Z are either hydrogen or lower aliphatic groups containing not more than 6 carbon atoms. x is a small whole number not greater than three. A is thc anion of polycarboxylic acid of the types previously discussed.

A more preferred species of 1,2-substituted imidazoline polycarboxylic acid salt may be illustrated by Formula IV below:

/l n ornomon x where R and x have the same significance, as previously indicated, and A is the anion of a polycarboxylic acid containing at least 6 carbon atoms in chain length, and is preferably a polymerized fatty acid.

A more specific embodiment of Formula IV is Formula V:

V. NCII; A-

Collar-C N'CIII l 11 ClIzCIlaOII 2 wherein A is a polymerized fatty acid of the type listed in Table I.

In the structural formula shown, the hydrogen atom of the acid is shown as being arbitrarily attached to the nitrogen atom in the 1- position. This is done for the sake of convenience with it being understood that salt formations may occur on the 1 or 3 nitrogen atom of the heterocyclic ring.

1,2-substituted imidazoline polycarboxylic salts of the types with which this invention is concerned are disclosed in Sterlin U.S. 2,773,879, the teachings of which are incorporated therein by reference. For purposes of completeness and for a fuller understanding of the invention, Table II lists typical compounds useful as carburetor deicers.

TABLE II.-l,2-SUBSTITUTED IMIDAZOLINE POLYCARBOXYLIC SALTS Moles of Comp. Polycarboxylic Imidaz- No. l,2 Substitutcd Imidazoline Acid oline Per mol of Acid 1-ti'rhydroxyethyl)-2-hepta- Composition II, 2

decenyl imidazoline. Table I. 1-(2-hydroxyethy1)-2-heptadecyl Composition 1, 1

irnidazoline. Table I. I-(Z-hydroxyethy l)-2rbeptadecyl Sebacio 2 irnidazoline. 2-heptedeccnyl-4-rnethyl Azaleic 2 imidazoline. 1- (2-stearoylaminoethyl-2- Suberlc 2 pentadecyl imidazoline. 1-(2-(2-aminoethyD-arnino- Composition 1, 1

cghyD-bheptadecyl irnidaz- Table I. 0 me. IX zheptzidBCenyl-Q-imidazolinc Sebaeic 2 X l-(2-ethylstearate)-2-ethyl Composition I 1 imidazoline. T able I.

Salt formation is accomplished by adding the acid to the l,2-substituted imidazoline until a homogeneous product is formed. Where either starting material is a solid, heat is usually necessary to liquefy the ingredient to insure a homogeneous blend of the materials.

While the products may be used as produced, it is generally desirable to dissolve or disperse the salts into a hydrocarbon liquid carrier, which makes proportioning of the treatment into the hydrocarbon fuel a simple matter. Such solvents as benzene, xylene, toluene, heptane and the like are suitable for this purpose. The well known blends of fractionated aromatic petroleum based products are economical choices as solvents for the salts.

In order to demonstrate the utility of the invention, the following are given by way of example:

Example I The following tests were conducted to determine the eflicacy of the cimpositions of the invention as carburetor De-Icers. The following describes the test of apparatus and methods employed in performing these tests:

TEST EQUIPMENT DETAILED TEST PROCEDURE Test preparation.-Prior to starting the test, the following was performed:

(1) Drain engine fuel lines and carburetor. (2) Check thermocouple performance. (3) Stablize temperatures as follows:

(a) Underhood (air) 36i2 F. (b) Oil sump 361-4" F. (c) Water jacket 361-4" F. (d) Carburetor air 361-2" F.

(4) Establish 100% humidity.

(5) Remove fuel from cold storage and connect to fuel system.

(6) Start engine.

Test period.

(1) Accelerate to 1500 rpm, no load.

(2) Maintain 1500 r.p.m. for one minute.

(3) Reduce speed to idle. Allow 30 seconds idle time. If engine does not stall, repeat steps 1 through 3. During the 30 seconds period, note engine bucking" which would be indicative of ice formation, but without stalling. If engine stalls, record as such and restart engine immediately, repeating steps 1 through 3. Record idle time in seconds before stall occurs.

(4) Items 1 through 3 constitute one cycle. Repeat as many cycles as necessary until throttle plate temperature rises above freezing or until three cycles are completed without stalling indication.

(5) During the course of conducting items 1, 2, and 3, record throttle blade temperatures at the start of idle and at stall time, or end of idle. Record other temperatures (air, water and oil) immediately after idle.

BASE FUEL DATA Composition, percent by volume:

Oxidation stability, minutes 1440 6 Distillation, ASTM:

IBP, F. 86 10% evaporated, F. 108 20% 127 30% 145 165 186 208 230 252 292 End point, F. 358 Recovery, percent 97.0 Residue, percent 1.0 Loss, percent 2.0

TEST VARIABLES In brief, the operating conditions and procedures used for conducting the tests were as follows:

Conditions:

35 to 40 intake air humidity Continuous air circulation Procedure:

(1) Start cold engine (2) Accelerate to 1500 r.p.m. and maintain for one minute. i (3) Decelerate to idle rpm. and maintain for onehalf minute. Observe and record engine stalling characteristics. (4) If engine stalls, immediately restart and rerun the cycles described by items 1 through 3 above.

The engine, atmospheric conditions and operating procedure selected for these studies were each planned to emphasize icing conditions so that the reduction of ice formation indicated by an additive would be further reduced by several times under normal consumer conditions.

Except that the engine load and speed must be low, the selection of optimum speeds for carburetor icing tests was relatively flexible. In general, the throttle opening should be at a minimum adjustment for prolonged engine warm-up and for maximum throttle blade exposure to the moist air; and yet, the throttle must be sufficiently opened to cause adequate fuel flow through the carburetors primary jets so that freezing temperatures will result from vaporization of the volatile gasoline.

Engine speed to attain these conditions was established at 1500 r.p.m. and although ice formation began on the throttle blade at this speed, the engine seldom, if ever, stalled until the speed was reduced to idle. When decelerating from 1500 rpm. to idle, the air crack between the throttle valve and throttle body began filling with ice, shutting off air into the manifold. Just prior to stalling, the air fuel ratio became excessively rich and occasionally caused the engine to buck before stalling.

At temperatures below 35 F., the moisture content of the air is generally too low for the rapid build-up of ice necessary for stalling, but the maximum air temperature for stalling is not so well established because of the influence of fuel volatility and carburetor design. Usually, standard procedure during carburetor icing test is to maintain the air temperature at a constant level throughout the test, at perhaps 40 F. The temperature control technique used deviated from this standard procedure since, during exploratory studies, it was observed that some additive compositions were prone to cause irregular icing rates at different temperature levels.

After conducting preliminary studies at constant temperatures, it was decided to try simulating consumer conditons by starting with a minimum air temperature of 35 F. and then allow a gradual rise in air temperature to a maximum at which ice would no longer form. Although this latter procedure introduced the problem of maintaining a constant air temperature increase rate, it

appeared to provide a more valid, reproducible testing technique and was thus adopted as the procedure for these tests.

Humidity was maintained at, or near, 100% through use of a finely atomized water spray on the test cell cooling coils. Air circulation over these coils was held at a constant rate by means of a forced-air recirculating system.

SUMMARY OF umsUL'is Icing tests were conducted using Composition III, Table II dissolved in 50% by weight of xylene. The concentrations of this additive formulation tested were at 10, 25, 50 and 100 parts per million. The results of these tests are shown below in Table III.

8 Example III For purposes of comparison, isopropanol and dimethyl formamide were tested. It was found that these materials achieved effectiveness similar to the results obtained with the compositions of the invention, only when dosages in excess of the 0.5% were used. In the case of isopropanol, 2% was necessary to achieve satisfactory results.

Example IV Compositions IV-X were tested in several commercial automobiles using winter-grade fuels for a period of several months, under the winter conditions experienced in the Chicago, Illinois, area. Dosages were at 250 parts 1 Cycles during which a stall almost occurred, presumably due to icing, as indicated by "bucking."

I The total cycles required for a complete test of the fuel iuelutling stalling cycles,

bueking" cycles, and cycles (luring hich no icing was indicated. 3 Average of throttle plute temperatures at the time of stalling.

From the above, it will be seen that with 100 parts 30 per million.

per million of the additive (50 ppm. active), good deicing results were obtained. Some effectiveness was shown at 50 parts per million (25 ppm. active). The tests run at 10 and parts per million are not shown, since the results on the particular grade of fuel used were no better than the base fuel test without additive.

Example II The test procedure used in Example I was the same except that the automobile engine used was a 1957 production Buick engine. Composition III, Table II was made up into a 50% by weight xylene solution and was tested at 500 parts per million. Also tested at 500 parts per million were two commercial petroleum hydrocarbon additives for purposes of comparison. The results of these tests are given below in Table IV.

TABLE IV The drivers of these vehicles indicated they experienced no difliculty due to carburetor icing, and it was therefore concluded the compositions were elfective for purposes of preventing carburetor icing when added to motor fuel.

The expression, divalent organic radical as used herein is meant to cover an organic group having two free open positions.

As was indicated above, the term volatile winter-grade gasoline designates a gasoline at least of which distills over at 212 F. The gasoline can also be defined as having :1 Reid vapor pressure of at least 10 lbs/sq. in. at 100 F. and more preferably a Reid vapor pressure of 10.5 lbs/sq. in. at 100 F.

The invention is hereby claimed as follows:

1. The method of preventing carburetor icing during the operation of internal combustion engines which comprises operating said engines with a volatile winter-grade gasoline having a Reid vapor pressure of at least 10 lbs./ sq. in. at 100 F. which gasoline contains from 25 to 500 parts per million of 1,2-substituted imidazoline polycar- Av 50 Number of Number of Total Thrtfitle bQXyhc acld Salt h om the group conslstlng Fuel Sample Stall Bur-king" Test Ilute I H Cycles Cycles 1 Cycles 2 Temp l N-C-Y Base s 1 11 32 Additive A 7 I I0 33 Mic Additive B 5 8 1 II BI Composition III, H 7 Table II 3 0 I0 34 1 (I yeles during which a stall almost occurred presumably due to lein' asiudicatcd by "bucking." h II. II A- Z The total cycles required for a complete test of the fuel-including T g stalliug cycles bucking eyclcs, and cycles during which no icing was 1\ Y indicated. 3 Average of throttle plate temperatures at the time of stalling. RC\

N G II 4 2,4,G-(dlmethylumiuo methyl) phenol i Lecithin L Xylene. 5 One mo 10 D R X oxide Dibuty] Amiile c s I 10 III. II A ulropyl I ormeol (40% by weight IICIIO m u-propyl I (l Y alcohol) 8U RC Based on the above, it can be seen that 500 parts per million of the additive gave exceptional results as a de- I icer for a winter-grade gasoline, whereas the other addi- R X lives were ineffective.

wherein D is a divalent, nonamino, organic radical containing less than 25 carbon atoms composed of elements from the group consisting of C, H, and N, D represents a divalent, organic radical containing less than 25 carbon atoms composed of elements from the group consisting of C, H, O and N, and containing at least one amino group; R is from the group consisting of higher aliphatic hydrocarbon groups containing from to 23 carbon atoms and hydrogen, with the proviso that at least one occurrence of R is a higher aliphatic hydrocarbon group; Y and Z are from the group consisting of hydrogen and lower aliphatic hydrocarbon groups containing not more than 6 carbon atoms; at is a small whole number not greater than 3, and A is an anion of a polycarboxylic acid containing at least 6 carbon atoms and not more than 3 carboxylic acid groups, said polycarboxylic acid having a hydrocarbon structure to which said carboxylic acid groups are linked.

2. The method of claim 1 wherein A is an anion of a polymerized fatty acid containing at least two and not more than three carboxylic acid groups per molecule and which is formed by the addition polymerization of fatty acids containing at least two olefinic linkages.

3. The method of claim 1 wherein A is an anion of a polymerized fatty acid derived from the caustic fusion of castor oil in the manufacture of sebacic acid.

4. The method of claim 1 where A is the anion of sebacic acid.

5. The method of preventing carburetor icing during the operation of internal combustion engines which comprises operating said engines with a volatile winter-grade gasoline having a Reid vapor pressure of at least 10 lbs./ sq. in. at 100 P. which gasoline contains from to 500 parts per million of a 1,2-substituted imidazoline polycarboxylic acid salt of the formula:

N-CH: R-O

wherein R is a higher aliphatic hydrocarbon group containing from 5 to 23 carbon atoms in chain length, x is a small whole number not greater than 3, and A- is an anion of a p-olycarboxylic acid containing at least 6 carbon atoms in chain length and not more than 3 carboxylic acid groups, said polycarboxylic acid having a hydrocarbon structure to which said carboxylic acid groups are linked.

6. The method of preventing carburetor icing during the operation of internal combustion engines which comprises operating said engines with a volatile winter-grade gasoline having a Reid vapor pressure of at least 10 lbs./ sq. in. at 100 P. which gasoline contains from 25 to 500 parts per million of a 1,2-substituted imidazoline polycarboxylic acid salt of the formula:

wherein R is a higher aliphatic hydrocarbon group containing from 5 to 23 carbon atoms in chain length, and

A- is an anion of a polycarboxylic acid containing at least 6 carbon atoms in chain length and not more than 3 carboxylic acid groups, said polycarboxylic acid having a hydrocarbon structure to which said carboxylic acid groups are linked.

7. The method of claim 5 wherein A is an anion of a polymerized fatty acid containing at least two carboxylic acid groups per molecule and which is formed by the addition polymerization of fatty acids containing at least two olefinic linkages.

8. The method of claim 5 wherein A is an anion of a polymerized fatty acid derived from the caustic fusion of castor oil in the manufacture of scbacic acid.

9. The method of preventing carburetor icing during the operation of internal combustion engines which comprises operating said engines with a volatile winter-grade gasoline having a Reid vapor pressure of at least 10 lbs./ sq. in. at 100 F. which gasoline contains from to 500 parts per million of a 1,2-substituted imidazoline poiy carboxylic acid salt of the formula:

wherein A- is a polymer fatty acid containing an average of about two carboxyl groups per molecule and R is a higher aliphatic hydrocarbon group containing 5 to 23 carbon atoms.

10. The method of preventing carburetor icing during the operation of internal combustion engines which comprises opertaing said engines with a volatile winter-grade gasoline having a Reid vapor pressure of at least 10 lbs./ sq. in. at P. which gasoline contains from 50 to 500 parts per million of a 1,2-substituted imidazoline polycarboxylic acid salt of the formula:

II IIzUIIzOII 2 wherein A is an anion of a polymerized fatty acid derived from the caustic fusion of castor oil in the manufacture of sebacic acid.

11. A method as in claim 1 wherein said volatile winter-grade gasoline has a Reid vapor pressure of at least 10.5 lbs/sq. in. at 100 F.

References Cited by the Examiner UNITED STATES PATENTS 2,553,183 5/1951 Caron et al 4471 2,668,100 2/1954 Luvisi 44-63 2,773,879 12/1956 Sterlin 4463 X 2,915,376 12/1959 Raifsnider 4463 2,945,821 7/1960 Sterlin' 252392 DANIEL E. WYMAN, Primary Examiner,

Y. M. HARRIS, Assistant Examiner. 

1. THE METHOD OF PREVENTING CARBURETOR ICING DURING THE OPERATION OF INTERNAL COMBUSTION ENGINES WHICH COMPRISES OPERATING SAID ENGINES WITH A VOLATIVE WINTER-GRADE GASOLINE HAVING A REID VAPOR PRESSURE OF AT LEAST 10 OLBS./ SQ. IN. AT 100*F. WHICH GASOLINE CONTAINS FROM 25 TO 500 PARTS PER MILLION OF 1,2-SUBSTITUTED IMIDAOLINE POLYCARBOXYLIC ACID SALT FROM THE GROUP CONSISTING OF: 